Carbohydrates of pigeon milk and their changes in the first week of secretion

The carbohydrate content of pigeon crop secretion called pigeon milk (PM) was in the range
of 0.9-1.5%. Sugars of trichloroacetic acid soluble (TCA-S) fraction increased by 67% between
day-1 and day-5 of secretion while those of TCA- insoluble (TCA-P) fraction remained fairly
constant. Sialic acids constituted 59% of carbohydrates. The proportion of lipid- and proteinbound
sialic acids was 5 1070 and 3 1 Yo respectively; the former increased from 41 070 to 68% between
day-1 and day-5 whereas the latter decreased from 45% to 21 070 during the corresponding
period. Some of the sugars of PM were fucose (40%), glucosamine (31%), galactose (12%),
mannose (9070) and glucose (8%). The free sugars whose content was very low (0.05%) included
fucose, mannose, glucose and some unidentified oligosaccharides. The proportion of lipid- and
protein-bound sugars was 31% and 63% respectively; the former decreased by 7% from day-1
to day-5 while the latter increased by 11 Yo during the same period. Gel chromatography of PM
confirmed the presence of sialic acids and glucosamine; the latter existed both in free and bound
form. The nature of changes in the carbohydrate composition of PM in the first week of secretion
was more quantitative than qualitative.